Field of the Invention
The invention relates to a light box with a film for altering the radiation characteristics
Background of the Invention
The current state of knowledge is as follows.
Radiation-reducing lights generally comprise a housing with a plurality of illuminants arranged in it. In the front, the housing is closed with a covering plate in the direction of radiation. Furthermore, a film is arranged in front of the illuminants in the direction of radiation, said film altering the radiation characteristics of the illuminants, for example homogenizing the emitted light or guiding it into a certain direction.
A film for homogenizing the emitted light may be required for example in the event that the illuminants arranged in the housing generate a plurality of light cones, which would subsequently cast a plurality of shadows if the light is used for instance as a work or machine light. To prevent this from happening, a so-called diffuser film is required, which diffuses the individual light-emitting cones by optical refraction and hence prevents the casting of individual shadows. Furthermore, said type of film can bring about the shaping of the light-emitting cones of the individual illuminants, for example by deflecting them to a certain angle of radiation.
The problem associated with high-energy illuminants is that the materials used for the light are expanding at different degrees due to their different coefficients of thermal expansion, thus inducing thermal stresses. Said thermal stresses may result in corrugation and blistering of the film, especially if the film is affixed on the covering plate or clamped into the housing, such that the luminous properties of the film are lost due to the high coefficient of thermal expansion a of the film, which ranges between 70 and 80×10−6 K−1. In comparison, the coefficient of thermal expansion of a housing made of aluminum is close to 23×10−6K−1 and between 3 and 4.5×10−6 K−1 with the used plates. Because of these major differences, in particular a strong expansion of the film can result in considerable structural warpage, i.e., blistering or corrugation.
Moreover, lights have been disclosed in which light spots with a high luminance, produced for example with LED illuminants, are slightly scattered or homogenized by the [satin finish] of the covering plate, albeit without preventing the casting of multiple shadows. Guiding the light through lenses arranged in front of the illuminants does not resolve this problem either.
The object of the present invention is to resolve the problems mentioned above.